Magnesium(Mg)alloys have received an increasing interest in the past two decades for their tremendous application potential.The strength and corrosion resistance levels of common Mg alloys are still relativity low,and...Magnesium(Mg)alloys have received an increasing interest in the past two decades for their tremendous application potential.The strength and corrosion resistance levels of common Mg alloys are still relativity low,and especially they are to be improved simultaneously.The addition of rare earth(RE)to Mg alloys is believed to be beneficial for both the strength and corrosion resistance,and some RE-modified traditional Mg alloys have been studied and some new RE-containing Mg alloys have been developed by now.However,further simultaneous improvements in both strength and anti-corrosion require a better understanding of the behavior and mechanism of RE in Mg alloys.In this review,the common influence mechanisms of RE on mechanical and anti-corrosion properties of Mg alloys are summarized,and the latest research progress of RE-containing Mg alloys with simultaneously improved strength and corrosion resistance are introduced.It is demonstrated that the research on high-strength and high corrosion resistant RE-containing Mg alloys is still immature,and some opinions and suggestions are put forward for the synergetic improvement of the strength and corrosion resistance of Mg alloys,so as to contribute to the further development of Mg alloys with higher performance.展开更多
The corrosion resistance and evolution of corrosion products in medium-carbon high-strength spring steels were investigated in a neutral salt spray(5 wt% Na Cl solution). A formation model of γ-Fe OOH and a transform...The corrosion resistance and evolution of corrosion products in medium-carbon high-strength spring steels were investigated in a neutral salt spray(5 wt% Na Cl solution). A formation model of γ-Fe OOH and a transformation model describing the conversion of γ-Fe OOH to α-Fe OOH were constructed. The results indicated that, at the initial corrosion stage, the corrosion resistance was gradually improved with the addition of Cr; however, with the addition of alloying element V, the corrosion resistance decreased. These results were attributed mainly to the initial corrosion stage being closely related to the matrix microstructure parameters such as grain-boundary character and dislocation density. After the rust layer was formed at a later corrosion stage, the corrosion resistance was reinforced with the addition of Cr and V because Cr strongly influenced the composition, structure, and morphology of the corrosion products. The results presented herein show that Cr was conducive to the transformation of γ-Fe OOH into α-Fe OOH. Moreover, V and Cr exhibited obvious synergy and were enriched in the inner layer of the corrosion products.展开更多
Rolling process based on the plastic deformation as a surface strengthening treatment was employed,aiming to improve the wear resistance ability and functional performance of the high carbon equivalent gray cast iron(...Rolling process based on the plastic deformation as a surface strengthening treatment was employed,aiming to improve the wear resistance ability and functional performance of the high carbon equivalent gray cast iron(HCEGCI).The microstructures and tribological performance of the untreated and rolled samples were characterized.In addition,the wear mechanism of HCEGCI samples was also studied via pin-on-disc tests.The experimental results show that the as-rolled samples possess the structure-refined layer of 15μm and work-hardened layer of 0.13 mm.In comparison with the surface hardness of untreated samples,the surface hardness of as-rolled samples increases by 84.6%(from 240HV0.1 to 443HV0.1)and the residual compressive stresses existed within the range of 0.2 mm.The wear rates of as-rolled samples were decreased by 38.4%,37.5%,and 44.4%under different loads of 5 N,10 N,and 15 N,respectively.The wear characteristics of the untreated samples mainly exhibit the peeling wear coupled with partial adhesive and abrasive wear.However,as for the as-rolled samples,the adhesive wear was limited by the structure-refined layer and the micro-crack propagation was controlled by the work-hardened layer.Therefore,the wear resistance of as-rolled samples can be improved significantly due to the low wearing degree of the friction contact zone.展开更多
The defect-free CoCrNbNiW high-entropy alloy coating was successfully prepared by laser melting deposition,and its microstructure and wear resistance were investigated.The results showed that the microstructure of CoC...The defect-free CoCrNbNiW high-entropy alloy coating was successfully prepared by laser melting deposition,and its microstructure and wear resistance were investigated.The results showed that the microstructure of CoCrNbNiW high-entropy alloy coating consisted of fee phase rich in Nb and fee phase including un-melted W particles and rich in Cr.Moreover,an amount of fee phase was formed at the middle and top of coating,while the bcc phase rich in Cr was formed at the bottom.Meanwhile,the un-melted W particles were diffusely distributed in the coating.Therefore,the microhardness of CoCrNbNiW high-entropy alloy coating was improved and was 2.78 times as high as that of substrate.The wear loss and wear rate of coating were 0.26 and 0.23 times higher than those of substrate,respectively.The wear resistance of substrate was obviously improved due to the preparation of CoCrNbNiW high-entropy alloy coating.展开更多
A high content silicon aluminum alloy(Al-25Si-4Cu-1Mg)coating was prepared on a 2A12 aluminum alloy by supersonic plasma spraying.The morphology and microstructure of the coating were observed and analyzed.The hardnes...A high content silicon aluminum alloy(Al-25Si-4Cu-1Mg)coating was prepared on a 2A12 aluminum alloy by supersonic plasma spraying.The morphology and microstructure of the coating were observed and analyzed.The hardness,elastic modulus,and bonding strength of the coating were measured.The wear resistance of the coating and 2A12 aluminum alloy was studied by friction and wear test.The results indicated that the coating was compact and the porosity was only 1.5%.The phase of the coating was mainly composed ofα-Al andβ-Si as well as some hard particles(Al9Si,Al3.21Si0.47,and CuAl2).The average microhardness of the coating was HV 242,which was greater than that of 2A12 aluminum alloy(HV 110).The wear resistance of the coating was superior to 2A12 aluminum alloy.The wear mechanism of the 2A12 aluminum alloy was primarily adhesive wear,while that of the coating was primarily abrasive wear.Therefore,it is possible to prepare a high content silicon aluminum alloy coating with good wear resistance on an aluminum alloy by supersonic plasma spraying.展开更多
The effects of the pre-deformation on the microstructure, mechanical properties and corrosion resistance of Al–Cu–Mg–Ag alloys were investigated by means of hardness tests, tensile tests, intergranullar corrosion(I...The effects of the pre-deformation on the microstructure, mechanical properties and corrosion resistance of Al–Cu–Mg–Ag alloys were investigated by means of hardness tests, tensile tests, intergranullar corrosion(IGC) tests and transmission electron microscopy(TEM), respectively. The results show that with the increase of deformation amount, the aging hardening rate increases while the strength of the alloy decreases and then increases. The sample with a pre-deformation of 6% possesses the highest tensile strength due to the refinedly and homogeneously distributed precipitations. The pre-deformation aging accelerates the heterogeneous nucleation of ? and θ′ phases at dislocations, and also refines the precipitations both in the grains and along the grain boundaries. The precipitation of ? phase is restrained while that of θ′ phase is accelerated in pre-deformed Al–Cu–Mg–Ag alloy compared with the sample without pre-deformation. In addition, the width of the precipitate free zone decreases with increasing the pre-deformation amount, leading to a narrower IGC passageway. This results in an enhanced IGC resistance of Al–Cu–Mg–Ag alloy treated by pre-deformation aging.展开更多
Nb/Ta multilayer films deposited on Ti6Al4V substrate with Nb and Ta monolayer thicknesses of 30 nm, 120 nm, and 240 nm were irradiated by a high current pulse electron beam (HCPEB) to prepare Nb-Ta alloyed layers. Th...Nb/Ta multilayer films deposited on Ti6Al4V substrate with Nb and Ta monolayer thicknesses of 30 nm, 120 nm, and 240 nm were irradiated by a high current pulse electron beam (HCPEB) to prepare Nb-Ta alloyed layers. The microstructure and the composition of the outmost surface of melted alloyed layers were investigated using a transmission electron microscope (TEM) equipped with an X-ray energy dispersive spectrometer (EDS) attachment. The Ta content of the alloyed surface layer prepared from the monolayer of thickness 30 nm, 120 nm, and 240 nm was ~ 27.7 at.%, 6.37 at.%, and 0 at.%, respectively. It was found that the Ta content in the alloyed layer plays a dominant role in the microstructure of the films. The hardness and the wear rate of the alloyed layers decrease with the increasing content of Ta in the surface layer.展开更多
Using ABAQUS software and cylindrical ellipsoid and body heat sources with a peak-heat-fluxattenuation function,a finite element model of the temperature field in the laser-arc hybrid welding of 4.5-mm BW300 TP wear-r...Using ABAQUS software and cylindrical ellipsoid and body heat sources with a peak-heat-fluxattenuation function,a finite element model of the temperature field in the laser-arc hybrid welding of 4.5-mm BW300 TP wear-resistant steel is proposed.The proposed model considers convection,radiation,molten pool flow,and heat conduction effect on temperature.A comparison of the simulation and actual welding test results confirms the reliability of the model.This welding heat-process model can provide the cooling rate at any position in the heat affected zone(HAZ) and can be used as a reference for the analysis of material properties and for process optimization.展开更多
The microstructure,mechanical properties and wear resistance of high chromium cast steel containing boron after different heat treatments were studied by means of the optical microscopy(OM),the scanning electron micro...The microstructure,mechanical properties and wear resistance of high chromium cast steel containing boron after different heat treatments were studied by means of the optical microscopy(OM),the scanning electron microscopy(SEM),X-ray diffraction(XRD),hardness,impact toughness,tensile and pin-on-disc abrasion tests.The results show that as-cast microstructures of boron-free high chromium steel consist of martensite and a few(Cr,Fe)7C3carbide,and the macro-hardness of boron-free high chromium steel is 55-57HRC.After 0.5mass% B was added into high chromium cast steel,as-cast structure transforms into eutectic(Fe,Cr)2B,(Cr,Fe)7(C,B)3and martensite,and the macro-hardness reaches 58-60HRC.High temperature quenching leads to the disconnection and isolated distribution of boride,and there are many(Cr,Fe)23(C,B)6precipitated phases in the quenching structure.Quenching from 1 050℃,high chromium steel obtained the highest hardness,and the hardness of high chromium cast steel containing boron is higher than that of boron-free high chromium steel.The change of quenching temperature has no obvious effect on impact toughness of high chromium steel,and the increase of quenching temperature leads to tensile strength having an increasing tendency.At the same quenching temperature,the wear resistance of high chromium cast steel containing boron is more excellent than that of boron-free high chromium steel.High chromium cast steel guide containing boron has good performance while using in steel bar mill.展开更多
To solve the problem of poor wear resistance in conventional Hadfield steels under medium and low stress,a new kind of steel with high silicon and high manganese Fe–17Mn–6Si–0.3C was designed and its wear resistanc...To solve the problem of poor wear resistance in conventional Hadfield steels under medium and low stress,a new kind of steel with high silicon and high manganese Fe–17Mn–6Si–0.3C was designed and its wear resistance was studied.The results showed that it exhibited better wear resistance than conventional Hadfield steel in both dry friction and abrasive friction.The better wear resistance of the new steel with high silicon and high manganese resulted from the stressinduced γ→ε martensitic transformation.展开更多
基金This work was supported by National Natural Sci-ence Foundation of China(51871069)Domain Foundation of Equipment Advance Research of 13th Five-year Plan(61409220118)Science and technology innovation ma-jor project of Ningbo City(2019B10103).
文摘Magnesium(Mg)alloys have received an increasing interest in the past two decades for their tremendous application potential.The strength and corrosion resistance levels of common Mg alloys are still relativity low,and especially they are to be improved simultaneously.The addition of rare earth(RE)to Mg alloys is believed to be beneficial for both the strength and corrosion resistance,and some RE-modified traditional Mg alloys have been studied and some new RE-containing Mg alloys have been developed by now.However,further simultaneous improvements in both strength and anti-corrosion require a better understanding of the behavior and mechanism of RE in Mg alloys.In this review,the common influence mechanisms of RE on mechanical and anti-corrosion properties of Mg alloys are summarized,and the latest research progress of RE-containing Mg alloys with simultaneously improved strength and corrosion resistance are introduced.It is demonstrated that the research on high-strength and high corrosion resistant RE-containing Mg alloys is still immature,and some opinions and suggestions are put forward for the synergetic improvement of the strength and corrosion resistance of Mg alloys,so as to contribute to the further development of Mg alloys with higher performance.
基金financially supported by the National Natural Science Foundation of China (No.51474031)
文摘The corrosion resistance and evolution of corrosion products in medium-carbon high-strength spring steels were investigated in a neutral salt spray(5 wt% Na Cl solution). A formation model of γ-Fe OOH and a transformation model describing the conversion of γ-Fe OOH to α-Fe OOH were constructed. The results indicated that, at the initial corrosion stage, the corrosion resistance was gradually improved with the addition of Cr; however, with the addition of alloying element V, the corrosion resistance decreased. These results were attributed mainly to the initial corrosion stage being closely related to the matrix microstructure parameters such as grain-boundary character and dislocation density. After the rust layer was formed at a later corrosion stage, the corrosion resistance was reinforced with the addition of Cr and V because Cr strongly influenced the composition, structure, and morphology of the corrosion products. The results presented herein show that Cr was conducive to the transformation of γ-Fe OOH into α-Fe OOH. Moreover, V and Cr exhibited obvious synergy and were enriched in the inner layer of the corrosion products.
基金Funded by the National Natural Science Foundation of China(No.51872254)the Yangzhou Hanjiang District Science and Technology Plan Project of China(No.HJM2019006)。
文摘Rolling process based on the plastic deformation as a surface strengthening treatment was employed,aiming to improve the wear resistance ability and functional performance of the high carbon equivalent gray cast iron(HCEGCI).The microstructures and tribological performance of the untreated and rolled samples were characterized.In addition,the wear mechanism of HCEGCI samples was also studied via pin-on-disc tests.The experimental results show that the as-rolled samples possess the structure-refined layer of 15μm and work-hardened layer of 0.13 mm.In comparison with the surface hardness of untreated samples,the surface hardness of as-rolled samples increases by 84.6%(from 240HV0.1 to 443HV0.1)and the residual compressive stresses existed within the range of 0.2 mm.The wear rates of as-rolled samples were decreased by 38.4%,37.5%,and 44.4%under different loads of 5 N,10 N,and 15 N,respectively.The wear characteristics of the untreated samples mainly exhibit the peeling wear coupled with partial adhesive and abrasive wear.However,as for the as-rolled samples,the adhesive wear was limited by the structure-refined layer and the micro-crack propagation was controlled by the work-hardened layer.Therefore,the wear resistance of as-rolled samples can be improved significantly due to the low wearing degree of the friction contact zone.
基金financially supported by the National Key R&D Program of China (No.2017YFB1103604)
文摘The defect-free CoCrNbNiW high-entropy alloy coating was successfully prepared by laser melting deposition,and its microstructure and wear resistance were investigated.The results showed that the microstructure of CoCrNbNiW high-entropy alloy coating consisted of fee phase rich in Nb and fee phase including un-melted W particles and rich in Cr.Moreover,an amount of fee phase was formed at the middle and top of coating,while the bcc phase rich in Cr was formed at the bottom.Meanwhile,the un-melted W particles were diffusely distributed in the coating.Therefore,the microhardness of CoCrNbNiW high-entropy alloy coating was improved and was 2.78 times as high as that of substrate.The wear loss and wear rate of coating were 0.26 and 0.23 times higher than those of substrate,respectively.The wear resistance of substrate was obviously improved due to the preparation of CoCrNbNiW high-entropy alloy coating.
基金This work was financially supported by the National Natural Science Foundation of China(Nos.51675158,51535011,and 51675531)the Natural Science Foundation of Hebei Province(No.E2016202325)the Beijing Municipal Natural Science Foundation(No.3172038).
文摘A high content silicon aluminum alloy(Al-25Si-4Cu-1Mg)coating was prepared on a 2A12 aluminum alloy by supersonic plasma spraying.The morphology and microstructure of the coating were observed and analyzed.The hardness,elastic modulus,and bonding strength of the coating were measured.The wear resistance of the coating and 2A12 aluminum alloy was studied by friction and wear test.The results indicated that the coating was compact and the porosity was only 1.5%.The phase of the coating was mainly composed ofα-Al andβ-Si as well as some hard particles(Al9Si,Al3.21Si0.47,and CuAl2).The average microhardness of the coating was HV 242,which was greater than that of 2A12 aluminum alloy(HV 110).The wear resistance of the coating was superior to 2A12 aluminum alloy.The wear mechanism of the 2A12 aluminum alloy was primarily adhesive wear,while that of the coating was primarily abrasive wear.Therefore,it is possible to prepare a high content silicon aluminum alloy coating with good wear resistance on an aluminum alloy by supersonic plasma spraying.
基金Project(E2013402056)supported by the Natural Science Foundation of Hebei Province,ChinaProject(QN2014002)supported by the Science and Technology Research Foundation of Hebei Education Department for Young Teachers in University,ChinaProject(51601053)supported by the National Natural Science Foundation of China
文摘The effects of the pre-deformation on the microstructure, mechanical properties and corrosion resistance of Al–Cu–Mg–Ag alloys were investigated by means of hardness tests, tensile tests, intergranullar corrosion(IGC) tests and transmission electron microscopy(TEM), respectively. The results show that with the increase of deformation amount, the aging hardening rate increases while the strength of the alloy decreases and then increases. The sample with a pre-deformation of 6% possesses the highest tensile strength due to the refinedly and homogeneously distributed precipitations. The pre-deformation aging accelerates the heterogeneous nucleation of ? and θ′ phases at dislocations, and also refines the precipitations both in the grains and along the grain boundaries. The precipitation of ? phase is restrained while that of θ′ phase is accelerated in pre-deformed Al–Cu–Mg–Ag alloy compared with the sample without pre-deformation. In addition, the width of the precipitate free zone decreases with increasing the pre-deformation amount, leading to a narrower IGC passageway. This results in an enhanced IGC resistance of Al–Cu–Mg–Ag alloy treated by pre-deformation aging.
基金Project supported by the National Basic Research Program of China (Grant No. 2013CB632305)the Guangdong Province University-Industry Cooperation Project of the Ministry of Education, China (Grant No. 2010B090400444)+1 种基金the Guangdong International Cooperation Projects, China (Grant No. 2010B050900003)the Guangdong Science and Technology Plan Projects, China (Grant No. 2010A070500002)
文摘Nb/Ta multilayer films deposited on Ti6Al4V substrate with Nb and Ta monolayer thicknesses of 30 nm, 120 nm, and 240 nm were irradiated by a high current pulse electron beam (HCPEB) to prepare Nb-Ta alloyed layers. The microstructure and the composition of the outmost surface of melted alloyed layers were investigated using a transmission electron microscope (TEM) equipped with an X-ray energy dispersive spectrometer (EDS) attachment. The Ta content of the alloyed surface layer prepared from the monolayer of thickness 30 nm, 120 nm, and 240 nm was ~ 27.7 at.%, 6.37 at.%, and 0 at.%, respectively. It was found that the Ta content in the alloyed layer plays a dominant role in the microstructure of the films. The hardness and the wear rate of the alloyed layers decrease with the increasing content of Ta in the surface layer.
文摘Using ABAQUS software and cylindrical ellipsoid and body heat sources with a peak-heat-fluxattenuation function,a finite element model of the temperature field in the laser-arc hybrid welding of 4.5-mm BW300 TP wear-resistant steel is proposed.The proposed model considers convection,radiation,molten pool flow,and heat conduction effect on temperature.A comparison of the simulation and actual welding test results confirms the reliability of the model.This welding heat-process model can provide the cooling rate at any position in the heat affected zone(HAZ) and can be used as a reference for the analysis of material properties and for process optimization.
基金Item Sponsored by National Natural Science Foundation of China(51274016)Natural Science Foundation of Beijing of China(2142009)Plan Item of Beijing Education Committee of China(KM201310005003)
文摘The microstructure,mechanical properties and wear resistance of high chromium cast steel containing boron after different heat treatments were studied by means of the optical microscopy(OM),the scanning electron microscopy(SEM),X-ray diffraction(XRD),hardness,impact toughness,tensile and pin-on-disc abrasion tests.The results show that as-cast microstructures of boron-free high chromium steel consist of martensite and a few(Cr,Fe)7C3carbide,and the macro-hardness of boron-free high chromium steel is 55-57HRC.After 0.5mass% B was added into high chromium cast steel,as-cast structure transforms into eutectic(Fe,Cr)2B,(Cr,Fe)7(C,B)3and martensite,and the macro-hardness reaches 58-60HRC.High temperature quenching leads to the disconnection and isolated distribution of boride,and there are many(Cr,Fe)23(C,B)6precipitated phases in the quenching structure.Quenching from 1 050℃,high chromium steel obtained the highest hardness,and the hardness of high chromium cast steel containing boron is higher than that of boron-free high chromium steel.The change of quenching temperature has no obvious effect on impact toughness of high chromium steel,and the increase of quenching temperature leads to tensile strength having an increasing tendency.At the same quenching temperature,the wear resistance of high chromium cast steel containing boron is more excellent than that of boron-free high chromium steel.High chromium cast steel guide containing boron has good performance while using in steel bar mill.
基金financially supported by the National Natural Science Foundation of China (Nos.50971095 and 51171123)the Natural Science Foundation for Young Scientists of Sichuan Province in China (No.2010A01-436)
文摘To solve the problem of poor wear resistance in conventional Hadfield steels under medium and low stress,a new kind of steel with high silicon and high manganese Fe–17Mn–6Si–0.3C was designed and its wear resistance was studied.The results showed that it exhibited better wear resistance than conventional Hadfield steel in both dry friction and abrasive friction.The better wear resistance of the new steel with high silicon and high manganese resulted from the stressinduced γ→ε martensitic transformation.
基金funded by Open Research Fund of State Key Laboratory of Precision Manufacturing for Extreme Service Performance, Central South University, China (No. Kfkt2020-01)Hunan Provincial Natural Science Foundation, China (No. 2021JJ40774)the Project of State Key Laboratory of High Performance Complex Manufacturing, Central South University, China (No. ZZYJKT2021-01)。